Trouble downloading phone carrier's app

Agreed. I have the SIM card, but apparently it's not working. I've had about a dozen chat sessions with them, been to the Apple store, and tried everything I can think of to get the phone activated. At one time I had the carrier's app downloaded via wifi (using their app is how they want you to activate the phone). Couldn't get it to work. Kept getting "server" errors. Their "specialists" team activated the phone from the back end (or so they say), but we still have no service. I took the phone to the Apple store and the tech there ran a diagnostic on it and declare the phone good. He suggested the SIM card was bad. I began to wonder, "Do they have the right phone number?" I gave it to them in one of the chat sessions. But when the phone first came up, it was showing an incorrect number. Now it shows no number associated with it. Nor can I get to the screen where I can "make it" be the correct number. It's all been very frustrating. Don't know what to do now except wait for the techs to again ensure the phone is activated before having them send me yet another SIM card. Hate to blather on about this, but I'm at my wits end. Thanks for taking the time to reply.